212 THE CEREBRUM. 



second, the interior fibers, a part of which form the internal medul- 

 lary lamina. Into the thalamus enter the medial fillet, the spino- 

 thalamic tract, a small part of the medial longitudinal bundle, 

 the brachium conjunctivum cerebelli and perhaps some other 

 tegmental fibers, all carrying common sensory impulses; they end 

 chiefly in the lateral nucleus, whence the cortical fillet proceeds 

 to the sensory area of the cerebral cortex. The thalamus also 

 receives fibers from the special sense paths, from the optic, 

 auditory, olfactory, and probably the gustatory (?), and gives 

 rise to fibers that continue in those paths to the special sense areas 

 of the cortex or as, in the case of the olfactory, to reflex centers. 

 It is also known that the thalamus is entered by a considerable 

 number of corticifugal fibers, especially through the occipito- 

 thalamic and temporo-thalamic radiations. The several bundles 

 of thalamic fibers are as follows: 



(1) The columna of the fornix, having pierced the thalamus, 

 descends to the corpus mammillare and terminates in its medial 

 nucleus, whence the bundle of Vicq d'Azyr, the thalamo-mammil- 

 lary bundle, rises and ascends to the thalamus. It ends in the 

 anterior nucleus. 



(2) The stria medullaris thalami (Fig. 64) from the hippocampus 

 and from the region of the olfactory triangle, terminates in the 

 nucleus habenulse and from this nucleus the fasciculus retroflexus 

 originates and descends to the interpeduncular ganglion. Both 

 "one" and "two" belong to the olfactory paths. 



(3) From the lateral surface of the thalamus issue two groups 

 of fibers which rise chiefly in the lateral nucleus. They are 

 common sensory in function: (a) The inferior one is the ventral 

 stalk (ansa peduncularis) (Fig. 70), which rises from the medial 

 and lateral nuclei and is in part relayed in the lentiform nucleus 

 under which it passes toward its destination. It proceeds through 

 the inferior lamina of the internal capsule and contributes fibers 

 to both the medullary laminae of the lentiform nuckus and to the 

 external capsule. Underneath the lentiform nucleus the ventral 

 stalk is divided into two horizontal laminae by a thin sheet of gray 

 substance. The upper lamina, the ansa lenticularis, is inter- 

 mingled with the striato-thalamic fibers and enters into the lenti- 



